The art is cognizant of the desirability of reducing air drag on the blunt, forwardly facing surfaces of truck bodies and trailers. A variety of air deflectors have been developed to accomplish this end. Examples include the devices shown in U.S. Pat. Nos. 2,514,695; 3,415,566; 3,866,967; 4,021,069; 4,030,779; 4,068,883; 4,098,534; 4,135,754; 4,210,354; and 4,310,192. The referred to patents all show air deflectors fastened to the forwardly facing wall of a truck trailer or a truck body. All of the structures shown present contoured or angled surfaces to the airstream impinging upon the deflector generally from the front as the truck moves down the highway.
Air deflectors must have a sufficient strength to withstand the force of the airstream directed against them. Such strength has been achieved in several ways. The deflectors shown in the patents referred to include deflectors made of intrinsically rigid material and inflated deflectors that employ air pressure within a bubble-like deflector to achieve the same purpose. U.S. Pat. No. 4,068,883 shows the use of a brace supporting a rigid, vane-like deflector from behind, the brace itself being rigid and supported by the cab and the front of the cargo compartment of a single chassis truck.
In addition to being subjected to wind pressures, such deflectors are often accidentally struck by solid objects. Thus, surrounding structures at a loading dock, garage doors, and the like may be struck by the truck. Deflectors made of overly rigid or nonresilient materials can be permanently damaged by even relatively minor blows.
High density polyethylene is a desirable material for molding air deflectors. It is inexpensive, durable, flexible and resilient enough to endure a considerable amount of impact and other physical abuse. However, an air deflector molded from high density polyethylene and made thin enough to be desirably inexpensive, resilient, and flexible may be subject to deformation by excessive wind forces on the highway. Furthermore, under certain circumstances, the flow of air past sideways or rearwardly oriented openings between the deflector and the parts of the truck on which it is mounted can aspirate air from the interior of the deflector, creating a slight vacuum that may encourage collapse or other deformation of the deflector when subjected to highway wind forces.